Currently most breast cancer patients with confirmed axillary lymph node metastasis (cN1) at diagnosis are candidates for neoadjuvant chemotherapy (NAC). The increased utilization of NAC can be attributed to practical clinical advantages. The increasing use of NAC has, however, introduced questions regarding appropriate loco-regional management, including the optimal surgical approach to the axillary lymph nodes.

According to current guidelines, patients presenting with cN1 disease and treated with NAC, still undergo axillary lymph node dissection (ALND). In forty percent of these patients, however, the investigators see a nodal complete pathological response (ypN0). In certain subgroups, triple negative breast cancer and Her2 amplified breast cancer, this percentage is even higher. The investigators would like to lessen surgical morbidity by performing a targeted axillary dissection. The investigators place a clip in the biopsy-proven lymph node metastasis at diagnosis. After NAC, the investigators perform a dual agent sentinel node procedure and remove the clipped node during the same surgery. When these lymph nodes are microscopically tumor-free, the investigators can abolish an ALND. Targeted axillary dissection after NAC for cN1 disease seems to have acceptable false negative rates in previous trials. The investigators would like to further define patients where an ALND can be safely omitted.

Inclusion Criteria:

• Patients diagnosed with cT1-3N1M0 breast cancer, histopathologically confirmed.
• Age greater than or equal to 18 years and less than or equal to 85 years.
• Necessity and agreement to neoadjuvant chemotherapy

Exclusion Criteria:

• Previous surgery ipsilateral axillary or radiation ipsilateral axillary / chest.
• Extranodal metastases M1
• cN2-3 status
• Breast cancer with direct invasion of chest wall and / or skin cT4
• Disease progression (clinical /radiological) under neoadjuvant treatment
• Pregnancy
• Presence of a pacemaker in the ipsilateral chest wall

Breast cancer patients with confirmed axillary lymph node metastasis (cN1) at diagnosis are candidates for neoadjuvant chemotherapy (NAC). Patients will be included in this study if they are diagnosed with cT1-3N1M0 breast cancer, histopathologically confirmed.